Saturday, February 27, 2010

PAK FA from technological POV


An interesting video about T-50 program was published by Russian 'Roscosmos TV'. The follow text is my translation to English:

Short acceleration – 200 m only – and the take-off is done! Other aircrafts can do this only from carriers. However, the Russian 5th gen fighter has a number of features allow it to take-off from a short horizontal airstrip. The 5th gen engine effectively provides it.
Ilia Fedorov, the Supervising Director of NPO 'Saturn', deputy general director of the Russian 'United Engine-building Corporation' (UEBC) tells about the difference of  t-50's engine: 
-         "It has different thrust, naturally different tuning control. The number of constructive differences allow better thrust with lower fuel consumption. And the most important – it has totally different system of control".


The new engine of NPO 'Saturn' for PAK FA is the evolution of an engine family marked by the index '117'. Its tests on 'Saturn's facility in Rybinsk can be seen on this video. It proved its characteristics on the 1st PAK FA prototype: the taking-off is very steep on the video.

Sergey Chemezov, the Director General of 'Rostechnology' state corporation (NPO 'Saturn' owner) says:
-         "The engine allows   long time supersonic fly without the afterburner. The thrust-vectoring is provided for better maneuverability".

The engine is the heart of a fighter, but the radar is its eyes and ears.  And the navigation system is like a 'vestibular system'. All these indispensible features of 5th generation were developed together with the fighter itself.
Sergey Chemezov, the Director General of 'Rostechnology' state corporation (NPO 'Saturn' owner) says:
-         "The sub-units of 'Rostechnology' Corp. are produced engines and different devices for different planes including of course  - PAK FA. I think they produce about 70% in this class of parts".
The pilots notice with pride: even the first prototypes have almost serial avionics.  They have 5 next years for elimination this 'allmost' by tests.
Boris Obnosov, Director General of 'Tactical Missiles Weapon' Corp., says:
-         "The intensity of the tests had no examples even in USSR era.  It due to the big numbers of devices (missiles) and shorten terms of development. As it was already declared by RuAF Commander General we are responsible to provide this plane as a weapon system".
It's not kind of 'demonstration aircraft' for an air-show, but the formidable universal weapon system: air-to-air, air-to-ground, short, medium and long range. R-73 – is the smallest but formidable air-to-air missiles. It's in modernization. It's a 'digital' missile like all T-50's weapon systems.
Boris Obnosov, Director General of 'Tactical Missiles Weapon' Corp., says:
-         "The obligate condition for 5th gen fighters like F-22 and PAK FA as well is intra-fuselage placement of missiles. It's provided for RCS reduction".
The American F-22 'Raptor' was considered invincible till T-50 appearance. F-22's constructive 'ideology' is stealthiness against ground-based radars. The 'Sukhoi's fighter 'ideology': to spot 'Raptor' early and to overwhelm it in the short range fighting. In fighting stealth vs. stealth the better radar will decide the winner.
Vladimir Zagorodny, Constructor General, the department Chief in NIIP 'Tikhomirov' says:
-         "We will be able to counter these stealth fighters and even win them in some duel situations".
Vladimir Zagorodny shows his team 'baby': the radar for the new fighter. Due to secrecy the door here is usually closed for press, but they did exception for us. The AESA has more then 1500 MMICs. This radar is named AFAR in Russian: the active phased antenna array. Five AESA radars over all airframe will detect the targets in any direction. 
Vladimir Zagorodny, Constructor General, the department Chief in NIIP 'Tikhomirov' says:
-         "I didn’t see such technology in 'Raptor' or F-35".

All T-50's electronics is netted in a unified intellectual complex, able to prompt pilot what to do in the fly. Indeed, the 5th gen fighter – is sometimes called 'flying computer'.   The part of the pilot work will be done by the computer.
Andrey Tyulin, Director General of 'Aviapriborostroyenie' concern, says:
-         "The avionics allow high precision flying to the needed point, successful using high precision weapon, and aircraft precise positioning in the air space".

Stealth technology means less IR emission and less metal in the airframe. Then, the engine blades must be hidden and the composites must be used broader.
Nikolay Vymornov, the Chief Technologist of NPK 'Composite' says:
-         "In F-22 and F-35 the use of composites in airframe is not less, then 40%. We are sure, in our PAK FA fighter the use of composites will not fall of this number".
 The new carbon-plastic composite was already developed specially for 5th gen fighters. The metal details are made with new technologies too. The plane will fly on critical and even super-critical fly regimes. So the special requirements for the materials are needed. It's OK now in Russia: our country is the biggest titan consructions supplier.
Sergey Chemezov, the Director General of 'Rostechnology' state corporation (NPO 'Saturn' owner) says:
-         "The titan alloys (of T-50) are manufactured in VSMPO 'Avisma' – the world biggest titan alloys and titan  products manufacturer".
The first flying prototype – is only a subject for testing. When T-50 appears in RuAF colors it probably will look rather different. However, the work done is not done in vain.

36 comments:

  1. Thank you Igor!
    GREAT stuff!
    Did I understand well that
    most of the avionics are ready
    already, to be used on the early prototype?
    Is that be cause they have been already tested on SU-35BM?
    Is it true that PAK FA & SU-35BM will use the same avionics?

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  2. >PAK FA from technological POV

    That posting made my day.

    ReplyDelete
  3. to PAK FA Fan
    Hi!

    1 - Yes
    2 - Yes
    3 - No, the final face will be more advanced, adopted for all-directional AESA, so cannot be just the same.

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  4. Hi Igor
    do you have any predictions
    or any comment on weather
    it will be possible to finish
    PAK FA for 2015?
    Is engine going to be ready and is it
    only Saturn make the engine or Salyut will be
    involved also?
    Excellent article thanks!

    ReplyDelete
  5. An Engine - is always the hardest part, considering many other experiences. So, I dont believe, the finally engine (17,5 t thrust with new gas-generator and reverse flow) will be ready in 2015. As many are expecting the first serial batch of PAK FA will fly with 15-15,5 t 'index-117' engine + TVS and IR reduction system.

    If Salyut is remained out of newborn UEBC corporation, its chances to take part in PAKFA engine development are not high. This question is not clear however, coz now two competitive engine-building groups are merged in Russia: United Engine-Building Corporation (Klimov, Saturn, Perm Engines, Ufa, Chernyshev, SNTK Samara and others) and Salyut+Omsk's 'Baranov'. Both are mainly owned by the state, so further merging in one united state company is under consideration.

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  6. Thanks for answering my question Igor!
    Would you tell me please do you see Russian
    sky well protected after 2015 with state of art weapons like PAK FA & S-500
    or there would be still potential danger
    present with USA pushing with their
    militarization of the space (in the clear intent to push the balance in American advantage)?

    Also if you have any comment how can Sukhoin menage to produce Super-Flanker and Pak Fa
    in sufficient numbers?Any new factory perhaps like it was already decided for Almaz-Antey?
    Thanks in advance!

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  7. dear igor, what a magnificent post. i would like to ask to you that the 2nd test flight which on 12th feb. the picture shows that the aircraft already have a paint from the first flight 29th jan. is it same a/c or no. 2 or other prototype where they made 3 prototypes?

    some critics lips is was photoshop or fake. i would much appreciate from your comment.

    cheers, mike.

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  8. to PAK FA FAN:

    The main danger for the balance is the American 'reverse potential' i.e. their wish to keep nuclear weapon carriers in storage or with conventional munition after new NPT agreement is signed. Naturally, for US is more easy to do so then for Russia due to obvious economic reasons. Then, in time of crisis they could return (or treat to return) the nuclear warheads back.

    Also they probably lie when say their AMD system uses 'direct kill' principle only. After initially 'direct kill' testing nobody can prevent them from equipping the interceptors with low power nuclear warheads and rise the efficiency of their ABM system drastically. So, S-500 must also be an universal system with the ability to hit intercontinental ballistic missiles, cruise missiles, and satellites together with ground targets, both in conventional and nuclear load. THus it could be deployed even near US coast if needed, with very flexible selection of the targets depending of situation and future NPT agreements.

    The aim is to make the American strategy of 'preventive strike' dubious if not leading to fiasco. Let's assume they go for 'preventive strike' on the Russian Nuclear forces, i.e. submarines, intercontinental missiles deployments, storages, communication and command centers etc military objects. What the remainders of Russian forces will do in answer? True! THey will strike the American cities... Now guess, who will be the winner after all? ;)

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  9. to Mike:

    They have built 3 prototypes already, between them only one is flying and the remained two - are intended for the ground tests, including crash tests. I'm not sure if they already painted the flying prototype but they're certainly going to do so.

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  10. Great post Igor.
    Regarding whether the aircraft will be "ready" by 2015 is actually a strange question.
    This aircraft will likely be in service for some time and will probably be fitted with several engines and radar and weapons upgrades.
    Most of the components have been worked upon for a very long time even though there was previously no money to actually produce it in numbers.
    The unification of most of the design bureaus should have the benefit of streamlining development so for example helmet mounted sights for new generation attack helos and 5th gen fighters can be linked with costs shared as one example.

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  11. Igor , what happened to Mig UCAV program Skat ?

    What other UCAV is under development in Russia from Sukhoi/Yakalov design bureau ?

    If you have enough information can you do a write up on Russian UCAV program ?

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  12. I would be interested in learning about the MIG UCAV programme as well.
    I remember someone saying it was cancelled but then I remember that person also stating the Hermes series of missiles were cancelled too.
    This says to me temporarily suspended as Hermes is better than anything in Russian service and there are no visible alternatives for it.
    Currently Ataka might be good enough but eventually when their radars are operating to full spec then they will need rather better ATGM than the ATAKA which is certainly cheap enough and the best stopgap option for the moment IMHO.
    Regarding other UCAVs check out this:
    http://okb-sokol.ru/cgi-bin/go-pl?i-43

    Note the low flight speed of this armed UAV?
    6,000m altitude is OK (at such height you probably couldn't see this UCAV from the ground let alone hit it with ground fire), and the range is good at 2,400km with a 15 hour endurance, but a flight speed of 120-240km/h means this bird will take time to get to where it is going to be operating.
    This is perhaps why Russian AF officials complain that domestic craft are not up to scratch.
    Most I have seen lack speed.
    Not impossible to fix of course.
    Sukhoi has the Zond series found here:
    http://www.sukhoi.org/eng/planes/projects/bpla/complex/

    Yak has these:
    http://www.yak.ru/ENG/PROD/new_rpv.php

    Irkut has these:
    http://www.irkut.com/en/services/projects/muas/

    Have seen a UAV based on a full sized glider aircraft on a video too, will try to find its name.

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  13. BTW while looking for UAV pages I stumbled across this:

    http://dinamika-avia.com/product/classifier/helicopter/detail.php?id=1065

    The top left image is of the pilots cockpit of the Mi-28N from an Mi-28Ns flight simulator...

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  14. There is also the Sukhoi S-62 project:

    http://www.abovetopsecret.com/forum/thread200297/pg1

    Have you heard anything about this Igor?

    ReplyDelete
  15. to Garry:
    ==Have seen a UAV based on a full sized glider aircraft on a video too, will try to find its name.==

    - Irkut-Da42 http://www.irkut.com/en/services/projects/muas/

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  16. to Austin:

    The Russian UCAV program is totally wrapped by secrecy, only UAV variants are allow for publishing. So we can only guess if one or other UAV can have UCAV 'brother'

    ReplyDelete
  17. to Garry:

    ... and Irkut-850 too http://www.irkut.com/common//img/uploaded/files/IRKUT-850_2010.02_eng.pdf

    ReplyDelete
  18. Putin: Russia To Build New Strategic Stealth Bomber

    Mar 1, 2010 - "MOSCOW (AP) - Prime Minister Vladimir Putin said Monday that Russia will build a new strategic bomber, a move that comes as the nation tries to upgrade its aging military arsenal. Putin said in televised remarks that work on the bomber must follow the development of a prospective stealth fighter, which made its maiden flight in January and was hailed by the government as a big step in military modernization efforts. "We won't limit ourselves to just one new model," Putin said at a government meeting that focused on military aviation. "We must start work on a prospective long-range aircraft, our new strategic bomber. The chief of the Russian long-range aviation, Maj. Gen. Anatoly Zhikharev, said earlier this year that a prospective new bomber must join the air force in 2025-2030. Zhikharev said the new aircraft should replace the Soviet-built Tu-95 and Tu-160 strategic bombers. No images of the prospective new Russian strategic bomber have been published, but some commentators said it might follow the design of the U.S. B-2 bomber, which also made its first flight more than 20 years ago." Link: http://www.breitbart.com/article.php?id=D9E61MKG2&show_article=1

    Wind Tunnel Image Of Model, Link:
    http://www.domain-b.com/aero/mil_avi/mil_aircraft/images%5Cflying_wing_aircraft_domain-b.jpg

    "Finally, there is an unconfirmed report that Russia already has a Tu-180 heavy bomber--a "stealth" one, most probably very similar to the B-2, at least judging from the photograph. Development of a "stealth" heavy bomber would have been consistent with the propensity of the Soviet military and defense-industrial leaders to match U.S. modernization; it is much less clear if this would be a preferred choice for Russia. For this reason, one would have solid ground to question the information." Link: http://www.nti.org/db/nisprofs/over/modern.htm

    ReplyDelete
  19. Putin: Russia To Build New Strategic Stealth Bomber

    Mar 1, 2010 - "MOSCOW (AP) - Prime Minister Vladimir Putin said Monday that Russia will build a new strategic bomber, a move that comes as the nation tries to upgrade its aging military arsenal. Putin said in televised remarks that work on the bomber must follow the development of a prospective stealth fighter, which made its maiden flight in January and was hailed by the government as a big step in military modernization efforts. "We won't limit ourselves to just one new model," Putin said at a government meeting that focused on military aviation. "We must start work on a prospective long-range aircraft, our new strategic bomber. The chief of the Russian long-range aviation, Maj. Gen. Anatoly Zhikharev, said earlier this year that a prospective new bomber must join the air force in 2025-2030. Zhikharev said the new aircraft should replace the Soviet-built Tu-95 and Tu-160 strategic bombers. No images of the prospective new Russian strategic bomber have been published, but some commentators said it might follow the design of the U.S. B-2 bomber, which also made its first flight more than 20 years ago." Link: http://www.breitbart.com/article.php?id=D9E61MKG2&show_article=1

    Wind Tunnel Image Of Model, Link:
    http://www.domain-b.com/aero/mil_avi/mil_aircraft/images%5Cflying_wing_aircraft_domain-b.jpg

    "Finally, there is an unconfirmed report that Russia already has a Tu-180 heavy bomber--a "stealth" one, most probably very similar to the B-2, at least judging from the photograph. Development of a "stealth" heavy bomber would have been consistent with the propensity of the Soviet military and defense-industrial leaders to match U.S. modernization; it is much less clear if this would be a preferred choice for Russia. For this reason, one would have solid ground to question the information." Link: http://www.nti.org/db/nisprofs/over/modern.htm

    ReplyDelete
  20. Thanks Tony, that would be the PAK DA that has been mentioned in the past that is to be developed by Tupolev.
    Most of the internet fan art is based on the T-4MS and similar platforms, which is rather ironic because they were mostly proposals made before the Tu-160 was developed and were obviously rejected at the time.
    I would expect something rather different from the B-2 simply because Russias requirements are not the same, though the flying wing planform has the dual advantages of low drag and small RCS.
    Considering its payload will be 5,000km range cruise missiles initially and possibly even longer or stealthier missiles in the future in the strategic role it will not need the level of stealth of the US B-2, which is clearly a first strike weapon.

    Igor, thanks, the UAV I was thinking of was the Irkut-850. The video I was thinking of is here:

    http://www.irkut.com/en/gallery/video/irkut-850/

    But it is not the same quality as the video I downloaded, the one I downloaded was twice the file size but the same viewing length.
    I got it from the old www.pwgs.com website which no longer works, but had lots of videos of Russian and Ukrainian military stuff.

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  21. I don't mean this as a slight on the hard work done on the PAK-FA but I find the project's priorities a little absurd.

    Why spend so much money and time on increasing the aircraft's manoeuvrability? It's widely accepted today that most air-to-air combat will likely be BVR. Even if it comes to WVR having Su-27/30 level of manoeuvrability should be more than enough against aircraft like F/A-22 and F-35 that have sacrificed manoeuvrability for stealth.

    The development team should instead focus its efforts on the key feature of 5th gen aircraft: stealth. The airframe shape still looks fairly un-stealthy. And what happened to the plasma stealth research that was going on some time ago?

    Lastly, I would not consider it advisable trying to beat the American design on the basis of 'superior radar'. The Americans were the first to develop AESA technology and are ahead of everyone else in that area. Their latest fighter radars can even perform offensive jamming and microwave attacks! There is no way the PAK-FA's radar will be superior.

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  22. BVR missiles are not perfect and being radar guided in most instances will be the least useful AAM when both sides are operating stealth aircraft.

    To fire BVR you have to detect targets at BVR.

    The point is that if you are going to use manouverability to evade a missile which do you think you have the best chance of outmanouvering... a short range thrust vector control heat seeker that sees a complete image of your aircraft and is aimed at your left wing specifically, or a long range much faster missile with small control surfaces for long range low drag flight near the end of its flight envelope?

    Regarding superiority of radars... you seem very sure.
    The strange thing is that when Soviet and US radars for tracking space objects was compared it was the Soviet radars that could reliably track much smaller objects at much longer ranges... the Americans had spent a lot more money than the Soviets did though.
    Go figure. Sometimes it comes down to talent and Physics and no country in the world can claim to corner the market in those things.

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  23. to Gautm:

    If maneuverability was not so important, think why the Americans have inputed so much to make the Raptor super-maneuverable? Like this, if there is no big rational to beat the adversary on the base of an advanced radar, why the Americans every time try to do so?

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  24. I thought the Raptor and F-35 were regarded as having inferior maneuverability compared to the Flanker?

    In today and tomorrow's air-to-air engagements maneuverability takes a backseat stealth, radar and BVR. I'm sure PAK-FA already has Su-30 levels maneuverability. The Russians should call it a day and focus their remaining efforts on the stealth aspect instead.

    As for radar, whatever advantage the Russians may have had at the end of the Soviet era was wiped away by the next 15-odd years of funding shortages. I think I'm not wrong in saying the F-35's sensor suite will be better in capability to what the PAK-FA will have. The Russians are bragging about it being an LPI while American vendors have long since crossed that milestone and are discussing terms like microwave attacks instead.

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  25. to Gautm:

    ==The Russians should call it a day and focus their remaining efforts on the stealth aspect instead.==

    - But if prolonging your logic about radar race, it's of no sense to compete with US too since they are 'way ahead' in stealthiness design...

    I think the opposite: the Russian do right when they try to implement all their best on PAKFA, putting some unsolved problems aside. For example it's a bit hard for Russian to make completely new flattened silos, so it can be delayed till the second stage of the project. Instead they have accented their efforts on the advanced radar system of combines K- and L-band radars. It's something that even doesnt exist in US.

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  26. Well, the US may be ahead in stealth as well, but that's an aspect that's as integral, if not more, to a 5th gen aircraft as the radar. Thus far there have been no details about the stealth features to be implemented aside from mere claims that it will be as stealthy as the F-35. Also compared to the F-22 or F-35 prototypes this one does not look very stealthy, with the exposed engines, the protruding square air intakes and the relative non-smoothness of the surface.

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  27. Gautm:

    About 'smoothness': give me plz a picture of so close-up as PAK FA allowed to be photographed and lets compare. You can compare PAK FA with F-35 in high res pics as well and there is no difference in 'smoothness', after all these are both made by same technology of riveting.

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  28. Gautm
    You talk about the F-22 and F-35 like they are proven designs.
    The only thing you have to base that on is information from where?

    Exposed engines?
    This aircraft is a prototype that has never had its designed engines fitted, what is the point of displaying a solution to hiding the engines if you know you might be going with different engines in the final production aircraft?

    This is only a prototype so nothing is set in stone.

    BTW you claim the US is ahead in AESA radars, how many wing mounted long wave radars do they have in service?

    Do you even appreciate the fact that the stealth applied to US aircraft is designed to combat X band radar waves and that the Russian K and L band radars will use a longer wave than that?
    A good comparison is a US soldier getting some coloured paints and painting his face to break up the shape of his face so he can hide in front of trees... he will blend in, but the people looking for him have a normal light scope and a scope that sees in a different frequency range... the different frequency range scope is a thermal imager (in this case shorter wavelength than visible light) that can't detect colour in the paint the guy applied to his face, but it can see the heat generated from his face clearly.
    He thinks he is invisible...

    Long wave radar is less effected by shaping because it can't see details like the shape of an aircraft, you just get a pulse that is reflected in all directions to show the presence of an object.

    For the PAK FA pilot and the Su-35S pilot for that matter a target on the wing radar that doesn't appear on the nose mounted x band AESA is probably something worth looking at with the IRST and reporting to other assets.

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  29. The F-22 and 35 are 'proven designs' in the sense that they represent third-generation stealth from a country that has decades of experience from such aircraft. Certainly far more 'proven' than the PAK-FA.

    And frankly I don't buy that the American stealth design only works against a particular type of radar. Especially considering that since the days of the F-111 these aircraft were supposed to escape detection from a wide range of ground-based SAM radars in different frequencies as well.

    And the exposed engines is a factor when you consider that both the F/A-22 and F-35 prototypes had that covered right from the start.

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  30. to Gautm:

    I didnt understand what you mean 'exposed' and 'covered' engine? The main IR radiation is from the nozzles backwards. The first way to reduce it - is flattened nozzles (F-22), the second one is to mix the hot flow with the cold outer air (planned for PAK FA). Where F-35 is standing here I wonder...

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  31. By 'exposed' I meant that the entire cylindrical cross-section of the engines is visible from above. There's no RAM shielding like in the Eurofighter's engines and there is also no arrangement whatsoever to cool the exhaust or otherwise lower the rear IR/Radar signature.

    The F-35 does have the exhause cooling feature. If you'll notice the rear opening is not a perfect circle but rather ellipsoidal.

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  32. to GAutm:

    I think you are wrong about exhaust cooling feature and 'ellipsoidal' nozzle on F-35. Have you some article about this?

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  33. Gautm, You mean proven in the sense that they operate with impunity over Moscow, or proven in the sense that previous aircraft made in the same country operated over third world countries and dropped bombs successfully.
    The F-22 is the worlds first stealth fighter so I don't see how it can be a third generation stealth fighter.
    The F-35 is less capable rather than more capable than the F-22 in the areas considered important to fighters.
    I would hope an aircraft in service and another aircraft nearing service entry would be more proven than a prototype like the T-50.

    Regarding detection, the U-2 is now the first aircraft Americans claim to be stealthy with claims it could not be tracked by radar. Then they claimed the SR-71 was also using stealth to stay safe from air defences, yet it was height and speed respectively that kept those aircraft relatively safe, with SR-71s being tracked from takeoff to landing... its flight performance making identification straight forward.
    Needless to say the first attack in Desert Storm was not by F-117s in downtown Bagdad, it was Apache helos attacking radar stations operating relatively long wave radars that might have been used to vector Mig-29s onto the F-117s for IRST based interceptions with guns and IR guided missiles.

    Once the radars were down the destruction of the communcations network made organised air defence near impossible... they could easily have done it with non stealthy aircraft or cruise missiles.

    F-117 flight paths were always carefully planned to avoid any radars that might spot them.
    When the planning got slack an F-117 got shot down.

    The exposed engine issue is not a problem for aircraft that are not changing engines.

    The PAK FA was designed to be slightly bigger than the Su-27 so the Al-41 is slightly bigger than the Al-31 in the Flankers. The 117 is an Al-31 with features of the Al-41. The final engine will be smaller than the Al-31 and more powerful. The problem was caused by the change in size of the PAK FA from slightly larger than a Flanker to slightly smaller.
    Besides, FLankers themselves have no issue with IR signature... most modern state of the art IIR heat seeking missiles don't go for hot spots now anyway... they create an image of the target and allow the pilot to target a specific part like the canopy. Do you really think exposed engines will make any difference at all in such a case?

    Do you understand the difference between a turbojet and a turbofan and the implications of both?
    If you want to supercruise then you need a hot exhaust. Ever since the introduction of the R-73 heat seeker missiles have not been tail chasers.
    The issue is mixing the exhaust and thrust vectoring can help. Square exhausts reduces thrust by 15% and is an enormous penalty to reduce IR signature. It was applied on the F-22 because it made thrust vector control in 2D easier. The Russians have 3D vector control, why reduce thrust to increase mixing of cold air on a turbo fan when increasing the cold air flow through the engine will have a similar effect. In fact putting fins in the cold air flow to block parts of it will upset the flow and probably lead to quicker mixing when needed.

    The main problem I think is that you see the exposed engines and you think they are hot, yet it is the core section of the engine that is hot and the outer area of the engine where the cold air flows as blown by the main fan section around the hot section.

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  34. Garry, while I give hats off to your superior technical knowledge, I disagree that the rear RCS/IR signature in the PAK-FA has no significance in its stealth capability, especially against IRSTs and heat-seekers.

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  35. @Gautm
    In design, whether it is for aircraft or tanks or shoes there are always options and each choice involves compromise.
    For example there is a huge conflict of interest in fighter design when it comes to powerplant.
    If you want to super cruise then you need a big hot engine high exhaust speed engine.
    40 years ago that hot spot generated by the afterburner made you a bit of a target for IR guided missiles. 40 years on and IR sensors have moved on much further than jet engines have.
    Watch any police tv show where a helo is used to track people at night. Those bright easily defined human shapes in the dark are not burning at 1,500 degrees like a jet engine, that is human skin temperature.
    These days you will certainly want to reduce IR signature, but IRSTs and heat seeking missiles no longer need to see the burning last fan blade in an afterburning jet engine to get a lock. IR missiles have been all aspect for more than 30 years. In other words an IR seeker can get a lock on an aircraft target from the front without even seeing the engines.
    Don't be fooled, a modern IR seeker/sensor is not a hot spot sensor, it sees heat, but it also sees cold. Most of the sensors are cooled to very low temperatures so even at 15km up at -70 degrees C an aircrafts skin is very much hotter than most sensors that will be looking for it.
    A super cruising F-22 might not be using afterburner but friction with the air will raise the temperature of some parts of its skin to well over 100 degrees C.
    Perhaps the real solution is for me to correct what you are saying to what I thought I was saying all along:
    You said:
    "I disagree that the rear RCS/IR signature in the PAK-FA has no significance in its stealth capability, especially against IRSTs and heat-seekers."
    I think I said:
    "I think that the rear RCS/IR signature in the T-50 first prototype(that hasn't got the engines it will have in the production version of the final aircraft) has no significance in the stealth capability of the aircraft that will enter Russian AF service, especially against IRSTs and heat-seekers. "

    360 degree stealth is not possible. 60 degree stealth in all frequencies is not even possible.
    We talk about shaping techniques so that the radar signal from radars is deflected by the careful shaping of the aircraft so that it goes everywhere except back to the emitting radar, that only works with high frequency directional radar. Radar wavelengths half a kilometre long can't see the shape of the target, they just bounce off and return. The Russians have been working on long wave radar greatly improving accuracy and efficiency to the point where today a very long wave radar can be used as a search radar to detect targets and IR missiles can be fired to the vicinity of the target and then it can start looking for targets. It will have a database of targets it can engage and if it detects any within range it will guide and hit that target.
    The technology with the IR seeker and a database of targets sounds a bit far fetched but that is normal for lock on after launch weapons... and you need lock on after launch weapons for 5th gen fighters because in the weapon bay there is no chance to get a lock on some targets... you need to fire them in a specific direction and let them find the target themselves.

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